Recently, a lot of car drivers use mobile phones, navigation systems, monitors, etc. by attaching them on the front windowpane, dashboard, etc. An adhesion device as illustrated in FIG. 1 is used to attach them. FIG. 1a shows the status before the adhesion device is attached on an adhesion surface and FIG. 1b shows the status after the adhesion device has been attached. Referring to FIG. 1a, the adhesion device (10) comprises a housing (12) and a suction plane (13). Above the housing (12) is a support connector for cradling a mobile phone, a navigation system, and so forth. The support connector is equipped with a lever (11). At the center of the suction plane (13), the suction plane (13) is connected with the lever (11) by a center element (not illustrated). When the lever (11) is pressed down, the center of the suction plane (13) connected with the lever (11) is pulled toward the housing (12), resulting in a curved shape as illustrated by the broken line in FIG. 1b. Consequently, the inner space between the suction plane (13) and the adhesion surface is expanded, resulting in a lower air pressure between the suction plane (13) and the adhesion surface than the atmospheric pressure and the attachment of the adhesion device (10) to the adhesion surface.
However, the conventional adhesion device (10) is disadvantageous in that, since air exists in the inner space between the suction plane (13) and the adhesion surface prior to attaching the adhesion device (10) as seen in FIG. 1, it is difficult to attain a strong adhesion force because it is not easy to lower the pressure inside the inner space close to vacuum by expanding the inner space. And, if the ambient temperature rises because of hot weather, etc., the temperature of the air inside the inner space increases and so does the air pressure inside the inner space, resulting in a weaker adhesion force and detachment of the adhesion device (10) from the adhesion surface.
Further, the conventional adhesion device (10) is attached only on a smooth surface like glass and it is difficult to fix the adhesion device (10) on a relatively rough surface like a dashboard. Particularly, it is not easy to attach the adhesion device on a curved, not flat, adhesion surface. The windowpane or dashboard of a car is not completely flat but curved and it is almost impossible to firmly attach the conventional adhesion device on such a curved surface.